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An Extension of Sampford's Method for Unequal Probability Sampling


Anton Grafström, Department of Mathematics and Mathematical Statistics, Umeå University, SE-90187 Umeå, Sweden.


Abstract.  Sampford's unequal probability sampling method is extended to the case that the inclusion probabilities do not sum to an integer. In this case, the sampling outcome is left open for exactly one randomly chosen unit and that unit gets a new inclusion probability. Three applications are presented. Two of them challenge traditional sampling routines. The simple Pareto sampling design, which was introduced by Rosén in 1997, is also extended. The extended Pareto design is shown to be close to the extended Sampford design.